This invention refers to a folding chair having a toggle joint device between the rear legs of the chair, the seat frame and the backrest frame, which is designed to keep the chair in a stable condition when open.
There are known folding chairs in which the seat and backrest frames are made from metal sections or tubes, and are articulated to front and rear legs which are connected to lateral armrests; in a number of known types, the articulations between the tubular frames consist of simple pins which, with the aid of suitable additional braces, permit the chair to open and to maintain such condition. However, this type of chair proves to be complicated in structure and somewhat unreliable in that the rear legs are likely to fold up, causing the chair to close and fall; moreover, the additional braces are usually placed close to the seat frame, with the danger of causing injury to the hands. A further known type of chair includes longitudinal grooves along the innner side of the rear legs, in which slides a respective stop pin, constituting the articulation between the seat and backrest. Apart from involving an additional machining operation, the use of grooves in the tubular legs weakens the chair structure thereby making it wholly unreliable, in that even the slightest deformation of the legs and, consequently, of the grooves themselves, could cause the pins to come out, damaging the chair irreparably.
An object of this invention is to provide a folding chair, of the type described, but which is simple in structure and reliable in use, in that it does not present weakened parts, and which remains stable in the open position, with no danger whatsoever for the user.